Thermostat



March 18, 1941.

E. s. CORNELL, JR

THERMOSTAT Filed Jan. 5, 1938 INVENTOR TTORNEY Edwa ml 5. Corne H Patented Mar. 18, 1941 UNITED STATES PATENT 'OFFICE 4 Claim.

This invention relates to thermostatic control devices.

More particularly, this invention relates to electric-circuit-breaking switches or thermostats of the "bi-metallic type, in which two electrically conductive members, one of them bi-metallic, are brought into or out of currentconductive engagement by movement of such bimetallic member under the influence of the unequal expansion of contraction of the metallic constituents thereof on change of ambient temperature. Advantageously, said members are provided with suitable electrical contact points, at least one being adjustable to make a greater or less movement of the bi-metallic element necessary to effect the make or break of the electrical circuit.

'It is an object of the present invention to provide a thermostat having a relatively small size, compact housing or supporting structure, in which the thermally-responsive make and break device is mounted as a unitary structure, such make and break device therefore being removable, as a lmit, from such supporting structure.

A feature of the invention therefore is that the' temperature-sensitive circuit-breaking device may be inserted into and removed from the complete thermostat structure as a unit. Desirably, the bi-metallic and the fixed electrical conducting members are contained in a cartridge-like mounting, formed from electrically insulating material, and preferably embodying spaced insulating side walls which aiford ventilation of the thermostat elements and form means whereby the operator may grasp the thermostat unit during the insertion or removal thereof without exposure to electric shock.

An additional feature of this invention is that the stated electrically conductive elements of the thermally-sensitive cartridge project inwardly, and into suitable operative relationship with each other, from opposite ends of the stated cartridge. Suitable end extensions of such elements provide for screw-threaded attachment to insulated posts secured to the thermostat housing, advantageously to its stated cover portion; such posts thereby provide a rigid mounting for the cartridge and additionally form binding posts or equivalent points of connection to the electrical circuit. Such thermostatic unit is analagous, in facility of replacement or inspection,

to the familiar cartridge fuse.

the direction of radiated portion being removable with respect to a backmember or other mounting means, may be re placed or inspected without disturbing the thermostat mounting.

The thermostat structure lends itself to a va- 5 riety of uses, inclusive of a wholly enclosed structure for service under outdoor or other exposed conditions, a ventilated type of thermostat for indoor use, or a thermostat useful for controlling steam or other heat-pipe temperatures, the last mentioned use contemplating a saddle or equivalent structure arranged to be clamped to the heat-pipe and further arranged to support the removable cover in a manner providing for heat against the bimetallic element.

Desirably, the adjustable contact point may comprise a screw-threaded element. Such contact point may be externally adjustable, as by manipulation of a suitable knob, or may be adjustable only after the removal of the thermostat cartridge from the cover, the last mentioned form contemplating the use of the device for outdoor or other exposed service.

In the accompanying drawing:

Fig. 1 is a vertical section taken through an electrical thermostat embodying the present invention;

Fig. 2 is a front elevation, the cover portion 30 being partially cut away to expose the thermostat unit of the device of Fig. 1, such device representing a wholly enclosed thermostat suitable for outdoor or other exposed location;

Fig. 3 is a section taken through 3-3 of Fig. 2, 35 illustrating a method of clamping one of the thermostat elements between electrically insulating members of the thermostat cartridge unit;

Fig. 4 is a perspective of a thermostat cartridge unit made pursuant to the present inven- 0 tion;

Fig. 5 is a front elevation of a thermostat having a ventilated cover member, such thermostat being particularly suitable for indoor or roomtemperature control. A portion of the cover of the complete thermostat has been cut away to indicate the method of mounting such cover on a supporting back member;

Fig. 6 is a section taken through 66 of the thermostat of Fig. 5, particularly illustrating the temperature adjustment means thereof Fig. 7 illustrates the thermostat cover element, having secured thereto the unitary thermostat element, mounted in heat-control relationship to a heat-pipe; and

Fig. 8 is a perspective of the heat-pipe saddle or mounting of the structure of Fig. '7.

Referring to Figures 1, 2 and 4, the thermallyresponsive electrical cut-out switch or thermostat I0 includes a back member or mount II, a. cover I2 arranged to be removably secured thereto, and a temperature-sensitive electrical cutout device I4, the latter comprising a pair of electrical conducting elements I5, I6, suitably secured in proper operative relationship within a housing of cartridge-like shape. In the embodi ment of Fig. 1, the cut-out device I4 serves as a series connection between two electrical conductors I1, I8, of an electrical circuit.

The temperature-sensitive electrical cut-out device I4 is advantageously of the bi-metallic type, in which one of a pair of electrical conducting members, as l5, Fig. 1, is of laminated structure, the laminations generally being metals of dissimilar coefiicients of expansion. The stated metals are welded or otherwise unitarily combined. Upon the heating or cooling of the mem ber l5 under the influence of atmospheric temperature, for example, the unequal expansion of the metallic constituents thereof causes a warping or fiexing of the member. As is well known in the art, such bi-metallic element. may be employed as a thermally-responsive electrical make-and-break device by suitably positioning a free end thereof in proper relationship to a fixed member or electrical contact point, and connecting the respective fixed and bi-metallic elements in series connection in an electrical system, such for example, as the electric circuit of an oil burner motor or the like.

In the present invention, the bi-metallic member I5 and the fixed member I6, are rigidly mounted within the cartridge-like housing, the latter advantageously comprising a pair of suitably spaced walls 20, 2|, of electrically non-conducting material such as Bakelite, hard rubber, molded fibre, or the like, such walls being held together in a manner confining the thermostat elements by, for example, the tightly fitting metallic rings 22, 22, which encircle the ends of the walls; As clearly indicated in Figs. 3 and 4, the end-portions of the walls preferably abut, and grip the respective elements I5, l6 at a point intermediate the ends of such elements. Advantageously, and as illustrated in Fig. 1, the elements I5, I6, in the area of their contact with the end portions of the side walls 20, 2|, are given an off-set or step formation, such formation serving to prevent lateral displacement of the members I5, I6 with respect to the confining wall members 20, 2|. Obviously, the end-portions of such walls 20, 2| are suitably grooved to ac- (licsimlriodate the stated off-sets of the members As clearly illustrated in Fig. 1, the member I6 may beof a single thickness of metal, and secured by the side wall members 20, 2I both at the area intermediate its ends, and at a terminal end. Such member I6 is therefore relatively immovably mounted within the cartridge-like housing of the complete structure I4. On the other hand, the bi-metallic member I5 is secured in such manner that a free end thereof is disposed suitably intermediate the ends of the cartridge, and in suitable relationship to the fixed member I6 Advantageously, the stated elements I5. I6 are provided with electrical contact points 25, 26, of silver, stainless steel, or other material capable of readily conducting electricity, and substantially non-corrosive in character.

As indicated in Fig. 1, the contact 25 may be in the form of a button rigidly secured, as by welding, to the bimetallic member I5. Contact 26 may advantageously be a suitable screw, the end portion of which is tipped with the stated electrically con a suitable spring pressure against the sides of the screw 26.

The screw 26 provides for adjustment of the temperatures at which the make and break occurs, by establishing the amount of movement or flexing of the free end of the bimetallic element I5 necessary to make or break the electrical circuit.

As indicated in Fig. 1 and Fig. 7', the thermostat cartridge I4 is advantageously mounted within the thermostat housing II, I2, by securement to the cover I2 thereof,v such securement being effected through the agency of screwing the end-portions I5a, I6a of elements I5, I6 to insulated posts 28, 28, the latter desirably being riveted, as shown, to the cover member. The insulated posts advantageously have screw thread ed metallic inserts 29, an end of which may advantageously be of area equal to that of the posts 28. Such posts 28 and inserts 29 serve a double purpose, namely, means of rigidly securing the cartridge I4 to the cover I2, and as binding posts at which the electrical connection may be completed. Fig. 1 illustrates the use of machine screws in effecting the electrical connection of the members I5, I6 with the respective conductors I'I, I8 and the mechanical securement of the cartridge per se. As will be obvious, the posts 28 may incorporate projecting studs, with which nuts or insulated female threaded elements may be employed to efiect the connection. A primary object is to make the thermostatic unit or cartridge I4 removable, as a unit, while additionally employing the mounting means therefor as electrical connection points.

It will be noted that the elements I5, I6 of the thermostatic unit project inwardly from opposite ends of the cartridge I4. Such arrangement, while not essential, is advantageous in that it provides for mounting the thermostat unit or cartridge at two comparatively widely separated points; the cartridge is therefore rigidly mounted, and not readily damaged by dropping or other rough handling of the assembled thermostat.

As indicated in the drawing, the structure is compact in design, Figs. 5 and 7 being approximately full-scale illustrations of a preferred commercial embodiment of the invention. The dimensions of the completed thermostat will depend, in large degree, upon the current-carrying capacity of the unit, and in any event, should be of sufficient size to permit the insertion of the wires I'I, I8, with a portion of their common covering, as shown in Fig. 1, into the housing with sufflcient slack of the stated wires to permit the ready positioning or removal of the cover portion l2.

It is a feature of this invention that the structure is adaptable to a variety of uses and purposes. For example, the structure disclosed in Figs. 1 and 2 has particular adaptability for use in exposed locations, such as in the open air, in refrigerating rooms, steam rooms, etc; in con- Gil aasacev formity with such service, the cover it may be imperforate and tightly fitting with respect to the mount or back member H. As indicated in Fig. l, the cover 52 may be secured to the mount H by clipping the same over suitable spring clip members 36 of the mount, the members 30 having a depression adaptable to engage and retain suitable beaded portions of the cover. In the embodiment shown, the base ll may be secured, to a wall or the like by means of screws it. It is within the contemplation of this invention to have the posts 28 secured to the stated mount ll, thus making it feasible to secure the cover it to the mount by a screw threaded connection therewith. Such construction would find particular aptitude in a thermostat for use in extremely exposed or damp locations. Generally, the structure of Fig. 1 meets requirements for normal service.

Referring now to Figs. 5 and 6 an embodiment of the invention is illustrated as having its cover provided with ventilations 32, thus exposing the cartridge It to the free play of surrounding air,

'member, as previously described, having an extended shank, 33, projecting through the cover of the thermostat unit and being provided with a suitable insulated knob 34, the latter being removably secured to the shank 33 as by the set screw 35. As is also indicated in Fig. 6, the cover is advantageously provided with a bushing 36 of insulating material, to obviate the possibility of a short circuit between the stated contact screw and the thermostat cover. As shown in Fig. 5, the cover may be marked with a suitable legend to indicate the correct direction in which the contact screw must be turned to efiect the desired temperature adjustment. It will be clear- 1y understood that the marking on the cover of the embodiment of Fig. 5, is purely representative. The direction of revolution of the screw is a function of the arrangement of the laminae of the member l5, and their respective coeflicients of expansion. Also, such marking and such arrangement of laminae may depend upon the ultimate service of the thermostat: for example, a thermostat the function of which is to make an electrical contact on decreasing temperature may be structurally difierent,' as represents the lamination of the bi-metallic element l5, from one in which the contact is to be made on rising temperature. Such arrangements are well known in the art, and per se form no part of the present invention.

Referring now to Figs. '7 and 8, there is illustrated a form of thermostat particularly suitable for use as an "aquastat or similar device for starting or stopping oil burners, automatic fuel burners, or the like, in response to the temperatures of hot water, steam, or other heating medium generated by such heat source. Structurally, the thermostatic unit may be similar to the embodiment of Fig. 5, in that an external setting deviceis provided. For mounting the thermostat on or against a heat pipe, 40, Fig. '7,

there is employed a novel saddle or other mount ing device M. Such saddle may comprise two elements 42, 43, advantageously stamped from sheet metal of suitable gage. The stated elements, as illustrated in Figs. '7 and 3, are suits bly configurated to be clamped tightly about the walls of the pipe 40, through the agency of suitable nuts and bolts 44. The member 43 of the clamp ll is provided with outwardly extending structures 45, advantageously provided with tongues having recesses 46 for the reception of and engagement with heading 3! on the cover member l2 of the thermostat. Such an arrangement is in conformity with the general object of the invention of having the thermostat struc ture include a mounting member and a cover member removably secured thereto.

It is a feature of the clamp 4! that the structures 45 thereof are formed with horizontally eigtending portions 41, such portions 41 combining with the side walls of the cover 2 to form a substantially box like structure which shields the thermostatic cartridge M from outside temperature influences, while serving to direct the radiiant heat flow from the pipe 40 against the bimetallic element [5. Such effect may be enhanced by the use of conventional pipe insulation, such as plastic asbestos, or the like, to conipletely close remaining side wall openings of the assembled structure.

It is to be noted from Figs. 2 and 4 that the side wall members 20, 2! of the cartridge II are suitably spaced to provide for free play of the bi-metallic element I5 and for the complete ventilation of the respective elements I5 and I6. Such ventilation is effective to dissipate any heat formed by the passage of electricity through the respective elements l5, l6, while attaining a. primary'desideratum of exposing all faces of the sensitive element I 5 to contact with the heatcontaining medium, such as atmospheric air or the like, under the temperature influence of which the movement of such element occurs. The side walls 20, 2| of the cartridge unit l4 serve to shield the element l5 from the adverse influence of cooling drafts or the like, and serve as electrically insulated members which may be grasped by an operator in effecting removal or insertion of such cartridge. Desirably the members I5, I 6 are of appreciably greater currentcarrying capacity than they will normally be called upon to handle, thus keeping the heating effect of such current passage at a minimum.

Whereas I have described my invention by reference to specific forms thereof, it will be understood that many changes and modifications may be made without departing from the spirit of the invention. I claim: 1. A thermostat, comprising the combination with a supporting structure, of a thermally responsive electrical switch unit removably se cured thereto; said. unit including a plurality of wallforming elements of electrical insulation material arranged to form a substantially quadrilateral housing in which abutting end walls and spaced side walls of said elements define an opening; a plurality of electricity conducting elements disposed within said opening and secured therein by engagement of such housing end wallswith said electricity conducting elements; one of said elements being bi-metallic and'having a free end portion freely movable within said housing and arranged to make or break electrical contact with another of said elements under the influence of changes in ambient temperature; said lectricity conducting elements projecting from the ends of said housing to afford means for efiecting connection with an electrical circuit and additionally serving as means for mounting said thermostat switch unit on said supporting structure.

2. A thermostat, comprising the combination with mounting means and removable cover means for said mounting, of a temperature-sensitive electric switch unit removably secured to said cover means, said switch comprising a housing composed of electrical insulation material and having closed end walls and spaced apart side walls to afiord a longitudinally extending open space defined by walls of insulation material, an electricity conducting element extending longitudinally of said housing, within said space and secured against longitudinal displacement therein by engagement with said end walls, the said element in the zone of its engagement with one of said housing end walls being characterized by an o'fi'set configuration affording engagement with said end wall in a plurality of planes, a temperature-sensitive bi-metallic electricity conducting element extending longitudinally of said housing in spaced relation with the side walls thereof and having a free end disposed in operative relation to said first-mentioned conducting element for electrical contact therewith, said bi-metallic element, further, having an oilset configuration intermediate its ends whereby it may be secured against longitudinal displacement within said housing by a multiplanar engagement with an end wall thereof, means operatively associated with one of said conductor elements to vary the extent of travel of said bi-metallic element before electrically contacting tits operatively associated element, each of said conducting elements extending, as an integral structure, through and beyond an end wall of said housing to provide for connection of said conducting elements into an electric circuit and afiording means for securing said switch unit to said cover means.

3. An electric thermostat as set forth in claim 2, the said supporting structure comprising a saddle arranged for clamping against a heat source, said saddle having temperature-sensitive switch supporting wall structures for shielding said temperature-sensitive switch from heating or cooling effect external of said heat source while directing radiant heat from said heat source to the temperature responsive element of said switch.

4. A thermostat, comprising the combination with a mounting, of a temperature-sensitive electrical switch unit removably secured thereto, said switch including a housing structure composed of electrical insulation material and having closed end walls and spaced apart side walls to afiord a longitudinally extending open space defined by walls of insulation material, an electricity conducting element extending longitudinally of said housing within said space from end wall to end wall and secured against displacement therein by engagement with said end walls, and a temperature-sensitive bi-metallic electricity conducting element extending longitudinally of said housing in spaced relation with the side walls thereof and having a free end disposed in operative relation to said first-mentioned conducting element for electrical contact therewith, said temperature-sensitive element being secured against longitudinal displacement within said housing by engagement of an integral portion thereof with an end wall of said housing, each of said electricity conducting elements extending, as an integral structure, through and beyond an associated end wall of said housing to provide for connection of said conducting elements into an electric circuit and affording means for securing said switch to said mounting.

EDWARD S. CORNELL, JR. 

